Application of preliminary stage of risk assessment procedure for agricultural soils: Area affected by flood as a case study

The objective of the study was to use different approaches for assessing potential ecological risk for agricultural soils affected by intensive flood. The agricultural territory of 7000 ha situated in the middle course of the Vistula river and waterlogged for over one month during flood episode in the year 2010 was chosen as a pilot area. Soil samples (n = 17) were collected from the upper soil layer of 0-30 cm. To answer the question whether the contaminants present in the flooded soils pose a risk to ecological receptors, the ecological risk assessment (ERA) procedure (screening stage) consisting of two lines of evidence (chemical LoE and ecotoxicological LoE) was used. The chemical LoE included combined risk resulting from the presence of contaminants such as zinc and polycyclic aromatic hydrocarbons (PAHs). The risk values calculated for the ecotoxicological LoE (based on the Microtox test results) were higher than the chemical LoE risk values. For majority (88%) of samples the calculated integrated risk (IR) factor values were below the acceptable risk limit (IR of 0.50) recommended for agricultural land-use. However, statistical evaluations indicate low precision of the IR parameter and the necessity of the careful treatment of the data. Application of the first screening stage of the ERA methodology enabled to delineate the territories of possible high ecological risk and specify of the area that needs further investigations. The results of ERA were compared with the evaluations based on EC50 or TU parameters, which allowed to classify all samples from flooded area as nontoxic. This was in line with the results of contaminant determinations: the concentrations of Zn and PAHs in soils were below the threshold limits for agricultural soils as specified in Polish regulations. The results of toxicity determinations were related to physicochemical properties of soils (texture and organic matter content), but were not directly linked to the total content of pollutants.